The present invention relates generally to fluid infusion systems, and more particularly to an improved flow metering apparatus for such systems.
The infusion of fluids into the human body is usually accomplished by means of an administration set in conjunction with metering apparatus which controls the rate of fluid flow through the set. Peristaltic-type metering apparatus, which function by repetitively compressing and expanding a section of tubing, have proven particularly attractive since they do not introduce the possibility of leakage or contamination into the system, while providing positive control of fluid flow through the system.
One form of peristaltic-type metering apparatus which is particularly well adapted for infusion applications is described in U.S. Pat. No. 4,155,362, issued to Thurman S. Jess on May 22, 1979, and assigned to the present assignee. Basically, this apparatus includes individually spring-biased rollers mounted on a stepper motor-driven rotor which compress tubing of an administration set against a stationary platen, and a spring-biased plunger which restricts the lumen of the tubing downline of the rotor to provide a back pressure against which the rollers must work. This back pressure prevents the release of dissolved gas in the tubing, assists in restoring the tubing to its original shape following compression by the rollers, and prevents uncontrolled gravity flow in the event of failure of the apparatus.
In many applications, such as where medication is being administered, it is necessary that the operation of the metering apparatus be very precisely controlled to infuse only a preset volume of fluid at a preset rate. Unfortunately, manufacturing tolerances encountered in the apparatus and tubing, particularly in the metering head, may introduce metering errors unique to individual units which must be individually compensated for. In some cases this has required the fabrication and installation of unique gearing between the stepper motor and the rotor, which undesirably added to the cost of the apparatus. The metering apparatus of the present invention incorporates a novel rate compensating circuit which automatically varies the rotation rate of the rotor to compensate for rate errors, thereby obviating the need for unique gearing for individual units.
Accordingly, it is a general object of the present invention to provide a new and improved system for infusing fluids into the human body.
It is a more specific object of the present invention to provide a new and improved metering apparatus for use in conjunction with an administration set for infusing fluids into the human body.
It is another object of the present invention to provide a peristaltic-type pump and control system which provides for accurate administration of a predetermined quantity of fluid at a predetermined rate.
It is another object of the present invention to provide a fluid metering apparatus which provides improved metering accuracy.
It is another object of the invention to provide a self-contained fluid metering apparatus which is simple and convenient to use.